3-Methylidene-beta-lactams as potential inhibitors of beta-lactamases. Part 1: Synthesis of alpha-substituted derivatives from imines by Reformatzky reaction with chlorotrimethylsilane, silylation and Peterson olefination.

A new variation of the Reformatzy reaction with use of I2/zinc and chlorotrimethylsilane in THF and a shortened work-up is described allowing the synthesis of a wide variety of substituted beta-lactams 3 in fairly good yield. These lactams are silylated according to the Peterson reaction yielding by reactions with appropriate carbonyl compounds E/Z-mixturs of the substituted 3-methylidene beta-lactams 7, 8 and 10. The isomers are separated by CC and completely characterized by spectroscopic methods, mainly 1H NMR spectroscopy.

[Corrosion behavior of different screws and posts in the root canal].

A series of extracted teeth with failures in their restoration by root canal posts or screws was examined for corrosive processes on these posts and screws. The teeth were ground who make metallographic specimens. By structural analysis, measurements of hardness and by roentgenfluorescence analysis the fabricates were identified and grouped into known metal groups for such posts and screws.

[Dental reconstruction with non-precious metal screws and posts].

A short review of the current methods for restoring destroyed dental crowns by mechanical retentive elements. The causes leading to failure in such restorations are mentioned in a short review of literature. Main causes are corrosive changes in posts and screws anchored in root canals.